Hydraulic pump structure



May 6, 1958 F. A. SHERMAN 2,333,225

HYDRAULIC PUMP STRUCTURE Filed Aug. 25, 1954 4 Sheets-Sheet 1 IN V ENTOR;

F1. am 4 SHE/may 4 TTOFNHS May 6,1958

F. A. SHERMAN HYDRAULIC PUMP STRUCTURE 4 Shee ts- Sheet' 2 Filed Aug.25, 1954 1 N V EN TOR.

FL 0 r0 4 Sum/4N y 6, 1958. F. A. SHERMAN HYDRAULIC PUMP STRUCTURE 4Sheets-Sheet 3 Filed Aug. 25, 1954 JNVENTOR. FLOYD ,4 Syn/v4 [BY 1ATTOAME'VS M y 1953 F. A. SHERMAN 2,833,225

HYDRAULIC PUMP STRUCTURE Filed Aug. 25, p54 .4 Sheets-Sheet 4 I1E=E| J oM r r, /70 M Z1 Z2 U INVENTOR. Ham 4 jymm/v A TTOP/VEVS United Statesatent HYDRAULIC PUMP STRUCTURE Floyd A. Sherman, Birmingham, Mich,assignor to Motor Products Corporation, Detroit, Mich, a corporation ofNew York Application August 25, 1954, Serial No. 452,169 Claims. Cl.103-161) This invention relates generally to pump assemblies and refersmore particularly to improvements in hydraulic variable displacementtypes of pump assemblies.

It is an object of this invention to provide a pump structure renderingit possible to deliver fluid at a subs-tam tially constant predeterminedpressure regardless of variations in the speed of rotation of the pump.

It isanother object of this invention to provide a pump structure of theabove type'which is compact in size and is composed of a relatively fewsimple parts capable of being inexpensively manufactured and assembled.

The foregoing as well as other objects will be made more apparent asthis description proceeds especially when considered in connection withthe accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view through a pump embodying thefeatures of this invention;

Figure 2 is a sectional view taken on the line 2-2 of Figure l;

Figure 3 is a sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a sectional view taken on the line 44 of Figure 1;

Figure 5 is a sectional view taken on the line 55 of Figure 1; and

Figure 6 is a fragmentary sectional view showing a modified form of pumpassembly.

The pump assembly selected herein for the purpose of illustration has abody 10 provided with a rear wall 11 having an axially extending annularflange 12 extending forwardly from the periphery thereof and form ing achamber 13 which may be and preferably is connected to a reservoir (notshown) for hydraulic fluid. The front side of the chamber 13 is closedby a cap 14 having the peripheral portion clamped to the front end ofthe flange 12 by studs (not shown) and having a centrally disposed hubsection 16 axially bored to receive a drive shaft 17. Therear end of thedrive shaft 17 is reduced in diameter to provide a shoulder 18 and isjournaled in a bearing 19 supported within a blind bore 20 formed in thewall 11. The shaft 17 is also journaled in the hub section 16 of the cap14 by a pair of ball bearings 21 supported in side by side relationshipwithin the hub section 16. The rear bearing 21 abuts apart 22 secured tothe shaft 17 within the chamber 13 and the front bearing 21 abuts ashoulder 23 formed by reducing the bore in the hub section 16.

The part 22 is fixed on the shaft 17 adjacent the shoulder 18 and isformed with a rearwardly extending annular flange 24 concentric with theaxis of the shaft 17 and having a bearing engagement with the wall 11 ofthe body 10. In cases where the wall 11 is formed of a relatively softmaterial, a plate or disc 25o-f wear re sisting material is inserted inthe front face of the wall 11 to provide a bearing surface for the rearside of the flange'24. The disc 25 is centrally 'apertured to receivethe bearing 19 and. for practical purposes is considered apart of thefront'wall 11 of the body 18. The flange 24 Patented May 6, 1958 isfashioned to provide a plurality of circumferentially spaced cylinders26 which extend radially through the flange 24 and are rectangular incross section. The rear sides of the cylinders are open and are closedby the front surface of the disc 25 or wall 11 of the body 10, as shownin Figure 5 of the drawings.

Supported in each cylinder 26 for sliding movement radially with respectto the axis of the shaft 17 is a piston 27 which is also rectangular incross section. The rear sides of the pistons 27 form in effectcontinuations of the rear end of the flange 24 and have a slidingbearing engagement with the disc 25 or wall 11 of the body 10..

The above structure is particularly advantageous from the standpoint ofeconomy in manufacture since it facilitates and simplifies the formingoperations.

The rear end of the flange 24 on the part 22 and the rear walls of thepistons are maintained in bearing engagement with the disc 25 or rearwall 11 of the body 10 by an adjusting nut 28 threadably supported inthe front end of the hub 16 and centrally apertured to receive the shaft17. The rear end of the nut 28 engages an enlargement 29 on the shaft 17and cooperates with the latter to provide an adjustment whereby the rearsurfaces of the flange 24 and pistons 27 are held in contact with thedisc 25 regardless of wear. A lock nut 30 is threadably mounted on thenut 28 in a position to engage the front end of the hub and therebyprevent accidental rotation of the nut 28.

Surrounding the outer ends-of the pistons 27 within the shaft 17 againstthe shoulder 18. An annular flange 36.

extends rearwardly from the periphery of the part 35 to the disc 25 andserves to close the radially inner ends of the cylinders 26. The innersurface of the annular flange 36 is recessed at the rear end of theflange to receive a closure disc 37 which is secured to the flange 36and cooperates with the part 35 to provide a closed annular space 38around the shaft 17. A ring 39 surrounds the shaft 17 within the space38 and the opposite ends of the ring respectively slidably engage thepart 35 and disc 37. The internal and external diameters of the ring 39are determined to enable floating of the ring radially within the space38 throughout a distance approximating the stroke of the pistons 27within the cylinders 26. The ring 39 is operatively connected to thepistons 27 by pins 40 which are respectively slidably supported withincircumferentially spaced openings extending radially through the flange36. The openings are so positioned that the inner the outer endsrespectively bear against the inner ends of the pistons 27. Theconstruction is such that the pins 40 cooperate with the floating ring39 and the cam ring 31 to move the pistons 27 inwardly and outwardly intheir respective cylinders 36 without the use of springs or equivalentmeans. Thus, the pistons are positively moved in 'both directions with aminimum amount of friction and reliable operation of the pump is assuredthroughout the life of the latter. 1

Formed in the front surface of the disc 25 are two arcuate passages 41and 42 concentric with the axis of the shaft 17 and positioned toregister with the radially inner ends of the cylinders 26 as the latterare rotated by the shaft 17. The passage 41 is an intake for fluid andn3 communicates with the reservoir or with a supply of hydraulic fluidthrough a port 43 formed in the wallll. The intake passage 41 is solocated with respect to the cam ring 31 that it registers with thecylinders 26 when the pistons 27 in the cylinders move radiallyoutwardly. As a result fluid is drawn into the inner ends of thecylinders 26 as the latter travel along the arcuate intake pas sage 41.The passage 42 is a discharge passage and communicates with the point orpoints of demand for high pressure fluid through a port 44 formed in thewall 11.

The passage 42 is so located with respect to the cam ring 31 that itregisters with the radially inner ends of the cylinders 26 when thepistons 27 are moved radially inwardly by the cam ring 31. Thearrangement is such that the fluid admitted into theinner ends of thecylinders 26 through the inlet passage 41 during outward movement of thepistons 27 is subsequently discharged under pressure through the outletpassage 42 by inward movement of the pistons 27;.

Due to the surface to surface contact provided between the disc andadjacent surfaces of the pistons 27 and flange 24 a seal is providedwhich reduces the escape of fluid into the chamber 13 to a minimum. Theescape of fluid along the shaft 17 is prevented by a seal 45 surroundingthe shaft 17 at the front side of the forwardmost ball bearing 21 andengageable with a shoulder 46 formed by reducing the bore extendingthrough the hub section 16.

As shown in Figure 3 of the drawings, diameterically opposite sides ofthe cam ring 31 are seated in recesses 47 formed in the body 10 and areprovided with flats 48 which slidably engage adjacent side walls of therecesses 47. Suitable retaining plates 49 are fastened to the body atopposite sides of the cam ring 31 and overlie the adjacent sides of thecam ring to maintain the latter in sliding engagement with the walls ofthe recesses. The above construction enables sliding movement of the camring 31 relative to the body 10 in a plane perpendicular to the axis ofthe shaft 17. As a result of this sliding movement of the cam ring 31,the degree of eccentricity of the inner surface of the cam rim may bevaried to alter the stroke of the pistons 27 in the cylinders 26 andthereby vary the pressure of the fluid displaced from thecylinders 26through the discharge port 44.

In the present instance, it is desired to maintain the pressure of thefluid at the pump discharge port 44 substantially uniform regardless ofvariations in the speed of rotation of the drive shaft 17, and this isaccomplished herein by automatically adjusting the cam ring 31 relativeto the body 10. As shown in Figure 1 of the drawings, the flange 12 isformed with a pair of radially extending bores 50 diameterically opposedwith respect to the cam ring 31 and having the outer ends closed byplugs 51. A plunger 52 is slidably supported in each bore 50 in a mannersuch that the inner ends of the plungers respectively engage flatsformed on the outer surface of the cam ring 31 in diametrically opposedrelationship. The spaces in the bores'50 radially outwardly of theplungers 52 respectively communicate with fluid ports 53 and 54.

The flow of fluid to the bores 50 is controlled by a sleeve valve 55having a casing 56 formed with an axially extending chamber 57 andhaving a spool 58 slidably mounted in the chamber 57. One end of thecasing 56 has a port 59 connected to the pressure outlet port 44 of thepump so that the pressure of the fluid discharged from the outletport 44acts on the outer end of the spool 58 tending to move the'latterinwardly in the chamber 57. This movement of the spool 58 is resisted bya coil spring 60 housed within the chamber. 57' at the inner end of thespool with one end engaging the spool and with the other end engaging apart 61 mounted on the casing 56. The force exerted on the spool 58 bythe spring 60 is variable by adjusting the part 61- and for this purposean adjusting screw 611 s provided. In practice, the spring 60 opposesinward movement of the spool tit) 58 with a force corresponding to apredetermined or specified pump outlet pressure.

The casing 56 also has a pair of ports 63 and 64 which communicate withthe chamber 57 and which are spaced from one another longitudinally ofthe spool 58. The port 63 has a fluid connection with the port 53, andthe port 64 has a fluid connection with the port 54. In addition, thecasing 56 has a drain port 65 which is connected to the reservoir (notshown) and communicates with the chamber 57 at points spaced from oneanother longitudinally of the chamber'57. A passage 66 is formed in thecasing 56 to one side of the chamber 57 and communicates at its outerend with the interior of the chamber 56 adjacent the pressure inlet port59. The inner end of the passage 66 communicates with the interior ofthe chamber 56 through a port 67 located in opposed relationship to theports 63 and 64 between the latter. A

The valve spool 58 has three enlargements 68 spaced equal distances fromone another lengthwise of the spool 58 for controlling the flow of fluidunder pressure through the valve 55. The arrangement of the enlargements68 and the relationship of the various ports to the enlargements aresuch that when a predetermined pressure exists at the pump dischargeport 44, the valve spool 58 is held by the spring 60 in an intermediateposition wherein the pressure port 67 is closed by the centerenlargement 68 on the spool 58. When the valve 55 is in the inoperativeposition thereof noted above, the cam ring 31 is in the position thereofshown in Figures 1 and 2 of the drawings or, in other words, is in aposition to aflord maximum eccentricity and, hence, imparts the maximumstroke to the pistons 27. However, should the pressure at the Outletport 44 of the pump become greater than the predetermined desiredpressure determined by the spring 60, the valve spool 58 moves inwardlyagainst the action of the spring 60 to connect the high pressure port 59to the port 64 and to connect the drain port 65 to the port 63. Sincethe port 64 in the valve casing 56 communicates with the port 54 in thebody 10 of the pump assembly, and since the port 63 in the valve casing56 communicates with the port 53 in the pump body 10, the plunger 52engaging the bottom side of the cam ring 31 (Fig. 1) moves inwardlytoward the drive shaft 17 and the opposed plunger moves. outwardly.Thus, the cam ring 31 is shifted relative tothe pump body 10 in adirection to reduce the degree of eccentricity relative to the. axis ofthe drive shaft 17. As a result, the. displacement of the pistons 27 inthe cylinders 26 is reduced and the pressure of the fluid at the outletport 44 is lowered. It will be apparent that if the pressure drops belowthe desired value, the valve spool 58 is moved outwardly by the spring60 to close communication between the ports 64 and 67, and opencommunication between the port 67 and the port 63. Also, the port 64 isconnected to the drain 65 so that the cam ring 31 is moved by the topplunger 52 in Figure 1 in a direction to increase the. degree ofeccentricity.

During normal operation of. the. pump, the valve spool 58 is in theposition thereof shown in Figure 1 of the drawings wherein the centerenlargement 68 is positioned between the ports 63 and 64 in closingrelationship to the. port 67. Thus, relatively slight movements of thevalve spool 58 in either direction efiects an adjustment of the cam ring31, and hence, a substantially constant pressure may be obtained .at thepump outlet port 44 regardless of variations in the speed of rotation ofthe shaft 17. e

The embodiment, of the invention shownin Figure 6 of the drawingsdiflersfrom the above-construction in that the cam ring 31 is fixed and,hence, the, adjusting means for this cam are omitted. However, provisionis made for preventing the pressure of the fluid at the outlet port 44from exceeding apredetermined value and this is accomplished byintroducing a leaf spring 70 between the adjusting nut 28 and theabutment 29 on the shaft 17. The arrangement-is such that-should thepressure of the fluid in the respective cylinders 26 exceed apredetermined value determined by the strength ofthe spring 70, thedrive shaft 17 along with the parts 22 and 35 moves axially forwardly toprovide a clearance between the front surface of the disc 25 and therear walls of thepistons 27. Thus, fluid may escape from the cylinders26 into the chamber 13 and the pump outlet pressure is correspondinglyreduced. In this connection, attention is called to the fact that theouter races of the bearings 21 have a sliding fit with the boreextending through the hub 16 and the inner races have a pressed fit onthe shaft 17. Hence, the end thrusts are transmitted to the shaft 17through the ball bearings 21 during axial adjustment.

What I claim as my invention is:

l. A pump assembly comprising a body, a part supported for rotationrelative to the body and having circumferentially spaced radiallyextending cylinders of rectangular section closed at the radially innerends and open at the radially outer ends, said part providing radialwalls for three sides of said respective cylinders, pistons ofrectangular section respectively slidably supported in the cylinders andcoacting therewith in defining pumping chambers radially inwardly of thepistons, said body having a bearing surface which constitutes a fourthside wall of said respective cylinders, being slidably engaged flatwiseby an adjacent side of said respective pistons, a cam ring encirclingthe radially outer ends of the cylinders beyond the pistons, means forholding the radially outer ends of the pistons into engagement with theinner surface of the cam, said holding means comprising pinsrespectively slidably supported in circumferentially spaced boresextending radially through the inner walls of the cylinders and havingthe outer ends respectively engageable with the inner ends of thepistons, a ring surrounding the axis of rotation of the rotatable partin a position to engage the radially inner ends of the pins andsupported by said part for floating movement radially with respect tothe axis of rotation of said part, the inner surface of the cam ringbeing contoured to effect successive movement of the pistons inwardlyandoutwardly in response to rotation of said part, thereby to dischargeand draw in fluid, respectively, in relation to said pumping chambers,an inlet passage positioned within the body to introduce fluid into thecylinders upon outward movement of the pistons and an outlet passage inthe body for'receiving fluid under pressure from the cylinders uponinward movement of the pistons, and means maintaining said part in endsealed engagement with said bearing surface.

2. A pump assembly comprising a body, a part supported for rotationrelative to the body and having circumferentially spaced radiallyextending cylinders of rectangular section closed at the radially innerends and open at the radially outer ends, said part providing radialwalls for three sides of said respective cylinders, pistons ofrectangular section respectively slidably supported in the cylinders andcoacting therewith in defining pumping chambers radially inwardly of thepistons, said body having a bearing surface which constitutes a fourthside wall of said respective cylinders, being slidably engaged flatwiseby an adjacent side of said respective pistons, a cam ring encirclingthe radially outer ends of the cylinders beyond the pistons, meansadjustably supporting said cam ring for shift in a plane perpendicularto the axis of rotation of said part, means for holding the radiallyouter ends of the pistons into engagement with the inner surface of thecam, said holding means comprising pins respectively slidably supportedin circumferentially spaced bores extending radially through the innerwalls of the cylinders and having the outer ends respectively engageablewith the inner ends of the pistons, 21 ring surrounding the axis ofrotation of the rotatable part in a position to engage the radiallyinner ends of the pins and sup ported by said part for floating movementradially with respect to the axis of rotation of said part, the innersurface of the cam ring being contoured to effect successive movement ofthe pistons inwardly and outwardly in response to rotation of said part,thereby to discharge and draw in fluid, respectively, in relation tosaid pumping chambers, an inlet passage positioned within the body tointroduce fluid into the cylinders upon outward movement of the pistonsand an outlet passage in the body for receiving fluid under pressurefrom the cylinders upon inward movement of the pistons, and meansmaintaining said part in end sealed engagement with said bearingsurface.

3. A pump assembly in accordance with claim 2, in which said adjustablecam ring supporting means comprises pressure responsive plungers mountedfor radial movement on said body in engagement with said cam ring, andspring biased valve means controlling the application of fluid pressurefrom said outlet passage to said respective plungers to actuate the samein response to .variation in pressure in said outlet passage.

4. A pump assembly comprising a body, a part supported for rotationrelative to the body and having circumferentially spaced, radiallyextending cylinders of rectangular section closed at the radially innerends and open at the radially outer ends, said part providing radialwalls for three sides of said respective cylinders, pistons ofrectangular section respectively slidably supported in the cylinders andcoacting therewith in defining pumping chambers radially inwardly of thepistons, said body having a bearing surface which constitutes a fourthside wall of said respective cylinders, being slidably engaged flatwiseby an adjacent side of said respective pistons, a cam ring encirclingthe radially outer ends of the cylinders beyond the pistons, said camring being fixedly supported by the body, means for holding the radiallyouter ends of the pistons into engagement with the inner surface of thecam, said holding means comprising pins respectively slidably supportedin circumferentially spaced bores extending radially through the innerwalls of the cylinders and having the outer ends respectively engageablewith the inner ends of the pistons, a ring surrounding the axis ofrotation of the rotatable part in a position to engage the radiallyinner ends of the pins and supported by said part for floating movementradially with respect to the axis of rotation of said part, the innersurface of the cam ring being contoured to effect successive movement ofthe pistons inwardly and outwardly in response to rotation of said part,thereby to discharge and draw in fluid, respectively, in relation tosaid pumping chambers, an inlet passage positioned within the body tointroduce fluid into the cylinders upon outward movement of the pistonsand an outlet passage in the body for receiving fluid under pressurefrom the cylinders upon inward movement of the pistons, and meansmaintaining said part in end sealed engagement with said hearingsurface.

5. A pump assembly in accordance with claim 4, in i which said lastnamed means comprises a spring yieldably urging said part against saidbearing surface.

References Cited in the file of this patent UNITED STATES PATENTS732,109 Patterson June 30, 1903 1,666,466 Peters Apr. 17, 1928 1,729,764Dinesen Oct. 1, 1929 2,179,071 Wiedmann Nov. 7, 1939 2,192,660 JohnsonMar. 5, 1940 2,195,812 Czarnecki Apr. 2, 1940 2,214,552 Ferris Sept. 10,1940 2,287,369 Anderson ..a June 23, 1942 2,311,162 Du Bois Feb. 16,1943 2,354,076 Tucker et al July 18, 1944 (Other references on followingpage) UNITED STATES PATENTS Rauch Nov. 9, 1948 Adams Apr. 4, 1950Harrington Sept. 15, 1953 De Lancey et a1 Feb. 16, 1954 OConnor et alNov. 22, 1955 OConnor et al Apr. 24, 1956 FOREIGN PATENTS

